Rotomolders face a dilemma when it comes to color. The most cost effective method of coloring their parts is to buy blends of raw pigments referred to as dry color. Dry color is known for being cost effective but is known to cause physical property loss at higher loadings. Use of dry color frequently yields unacceptable impact resistance, a key performance metric in the Roto Molding Industry. Another drawback of the dry color method is that the products are often brittle, and often contain a speckled appearance on the surface of the product or part. The alternative is more-costly pulverized precolored compounds, which allows for higher pigment loadings and better physical properties. The industry would clearly benefit from a third option providing acceptable impact performance without the cost penalty of using precolored compounds.
Larger dry color particulates can negatively affect finished part performance by encouraging stress cracking. The additional shear applied in the extrusion of precolored compounds reduces the size of these particulates. Significant cost is added in this process however, both in the compounding and pulverizing steps. Improved part performance comes at a significant cost penalty. Color suppliers have yet to provide a cost-effective alternative.